Why were Vietnamese called Charlie during the Vietnam War?

The US Military USES the "Phonetic Alphabet" on an everyday routine basis. Alpha, Bravo, Charley, Delta, Echo, Golf, Hotel, etc. This is used because over the radio, a letter "C" could sound like the letters "D", "E", "B", etc. The Viet Cong (VC) were referred to as "Victor Charley", or "Charley" for short. It was also used for "Commies" short for "Communists." The NVA were (over the radio), "November Victor Alpha." US killed in Action or Wounded in Action, would come over the radio thusly: "Uniform Sierra Kilo India Alpha", and "Whiskey India Alpha." Two NVA killed, would be reported over the radio as, "2 November Victor Alpha's Kilo India Alpha, this date over..."